CN113439100B - Method for preparing organooxysilane-terminated polymers - Google Patents

Abstract

The invention relates to a process for the preparation of Y- [ O-C (=O) -NH- (CR) of formula (I) ¹ ₂ ) _b ‑SiR _a (OR ² ) _3‑a ] _x (I) The process of the organooxysilane-terminated polymers (SP) is characterized in that in process step 1 at least one of the compounds of the formula (II) Y- [ OH] _x (II) a polymer (OHP) and at least one polymer of formula (III) o=c=n- (CR) ¹ ₂ ) _b ‑SiR _a (OR ² ) _3‑ (III) isocyanate functional silane (IS) with the proviso that the isocyanate functional silane (IS) IS used in such an amount that at least 1.05 isocyanate groups are present in the silane (IS) per hydroxyl group in the compound (OHP), followed by reacting, in process step 2, unreacted isocyanate groups of the silane (IS) with at least one of the groups of the formula (IV) R in the reaction mixture obtained in process step 1 ³ Alcohol (A) of OH (IV) and subsequently in process step 3, the reaction mixture obtained in process step 2 is passed through an evaporation unit (VD) in which the reaction mixture having a layer thickness of not more than 5cm is exposed to a pressure of at most 80 mbar and a temperature of at most 200 ℃, wherein the reaction mixture of formula (V) R ³ O‑C(＝O)‑NH‑(CR ¹ ₂ ) _b ‑SiR _a (OR ² ) _3‑a The Carbamatosilane (CS) formed in the second process step of (V) is at least partially evaporated and removed, wherein all groups and indices have the definition set forth in claim 1. The invention also relates to the use of said polymers for producing adhesives and sealants.

Description

Method for preparing organooxysilane terminated polymers

The invention relates to a process for preparing organooxysilane-terminated polymers and to their use for preparing adhesives and sealants.

Polymer systems with reactive alkoxysilyl groups, more particularly silane-terminated polyethers, are long-established systems. On contact with water or atmospheric moisture, these alkoxysilane-terminated polymers are able to condense with one another with elimination of the alkoxy groups even at room temperature. One of the most important applications of such materials is the preparation of adhesives, more particularly elastic adhesive systems.

Three different methods for preparing silane-terminated polymers are of particular importance in the preparation of commercial products. However, all three methods have their own specific disadvantages/problems:

1. Preparation of so-called silane-terminated polyurethanes from polyethers, diisocyanates and aminoalkyl-functional silanes. A disadvantage of this process is the simultaneous chain extension, since some of the diisocyanates used react via two isocyanate groups with the polyether molecules to form dimeric polymers of twice the molar mass. This leads to an increase in the polydispersity M _w /M _n and thus to a relatively high viscosity of the products in question relative to their average molar mass M _n . A high molar mass M _n is essential for achieving excellent mechanical properties in the cured material (e.g. high tensile strength combined with high elongation at break). In contrast, a low viscosity is desirable for maximizing the processing properties of liquid adhesives or sealants. The lack of an option for preparing silane-terminated polymers of as high a molecular weight as possible with simultaneously very low viscosity is therefore a serious disadvantage.

2. Preparation of silane-terminated polyethers by allylation of the terminal hydroxyl groups therein and subsequent hydrosilylation of the alkyl chain ends formed in the allylation. A disadvantage of this process is the fact that, in particular, the hydrosilylation does not proceed to completion, so that a high proportion of unsilanized chain ends is obtained, which are therefore also not crosslinkable. This is detrimental to the mechanical properties of the cured adhesives and sealants which can be prepared on these polymers.

3. Preparation of silane-terminated polyethers by reaction of the terminal hydroxyl groups therein with isocyanatoalkyl-functional alkoxysilanes. This process allows almost complete chain termination without concomitant chain extension and thus avoids the disadvantages of the above two systems. However, the problem is that the isocyanatoalkyl-functional alkoxysilanes required for this process are highly toxic, so it must be ensured that they are no longer present in the final product (i.e., the silane-terminated polymer).

The prior art describes various methods which allow this problem to be solved and any isocyanate residues to be avoided in the end product. In EP-A 1 535 940, the reactant ratios are selected so that the isocyanatosilane is completely consumed by the reaction under the specific reaction conditions chosen. However, this method is prone to errors, and even small metering errors can lead to excessive metered isocyanatosilane remaining in the silane-terminated polymers, or insufficient metered isocyanatosilane leading to unsilanized and therefore unreactive chain ends, with the end result that the mechanical properties of the adhesives and sealants prepared from these polymers are not sufficiently constant.

In order to solve these problems, EP-A 1896523 proposes to prepare silane-terminated polymers in a continuous process, wherein isocyanatosilanes are used in excess and any unreacted isocyanatosilane groups present are removed with isocyanate-reactive compounds (such as alcohols or amines) in a subsequent step. However, a disadvantage of this method is that the removal products of the reaction, monomeric carbamate-functional and/or urea-functional di- or trialkoxysilanes, remain in the reaction mixture, thus affecting the mechanical properties of the cured final product. Dialkoxysilanes have a plasticizing effect, while trialkoxysilanes increase hardness by virtue of their ability to increase network density.

With respect to the final product, ie the fully formulated adhesive or sealant, this may be desirable in certain circumstances, but it may also be undesirable.

From the point of view of the producers of silane crosslinking polymers, it is desirable in any case to be able to provide products which are essentially free of additional monomeric silanes, so that the formulator of adhesives or sealants has the greatest possible formulation freedom and can decide for himself whether he wants to add monomeric silanes to his specific end-use formulation and, if so, which monomeric silanes to add.

It was therefore an object of the present invention to provide a process for preparing silane-functional polymers which does not have the abovementioned disadvantages of the prior art, nor other disadvantages such as discoloration.

The subject of the present invention is a process for preparing silane-terminated polymers (SP) of formula (I)

Y-[OC(＝O)-NH-(CR ¹ ₂ ) _b -SiR _a (OR ² ) _3-a ] _x (I),

It is characterized in that

In a first process step, at least one polymer (OHP) of the formula (II) is reacted with at least one isocyanate-functional silane (IS) of the formula (III),

Y-[OH] _x (II)

O＝C＝N-(CR ¹ ₂ ) _b -SiR _a (OR ² ) _3-a (III)

Provided that the isocyanate-functional silane (IS) is used in such an amount that for each hydroxyl group in the compound (OHP) there are at least 1.05 isocyanate groups in the silane (IS),

in

Y is an x-valent polymeric group,

R may be the same or different and is a monovalent, optionally substituted hydrocarbon radical,

^R1 may be the same or different and is a hydrogen atom or a monovalent, optionally substituted hydrocarbon group,

^R2 may be the same or different and is a hydrogen atom or a monovalent, optionally substituted hydrocarbon group,

x is an integer from 1 to 50, preferably 1, 2 or 3, more preferably 2,

a may be the same or different and is 0, 1 or 2, preferably 0 or 1, and

b may be the same or different and is an integer from 1 to 10, preferably 1, 3 or 4, more preferably 1 or 3, more particularly 1,

Subsequently, in a second process step, the unreacted isocyanate groups of the silane (IS) are reacted in the reaction mixture obtained in the first process step with at least one alcohol (A) of the formula (IV)

R ³ OH (IV),

in

^R3 is a hydrocarbon group having 1 to 4 carbon atoms,

and subsequently, in a third process step, the reaction mixture obtained in the second process step is passed through an evaporation unit (VD), in which the reaction mixture with a layer thickness of not more than 5 cm is exposed to a pressure of up to 80 mbar and a temperature of up to 200° C., wherein the carbamatosilane (CS) of the formula (V) formed in the second process step is at least partially evaporated and removed.

R ³ OC(=O)-NH-(CR ¹ ₂ ) _b -SiR _a (OR ² ) _3-a (V)

where all variables have the above definitions.

The content of carbamatosilanes in the reaction mixture obtained after the process of the invention is preferably at most 0.3% by weight, more preferably at most 0.2% by weight and very particularly at most 0.1% by weight, in each case based on the total weight of the reaction mixture.

The carbamatosilane content here is preferably determined by the method described in Example 2.

The evaporation unit (VD) used in the present invention may comprise any existing evaporation unit, such as preferably a thin film evaporator, a falling evaporator or a short path evaporator.

In the third process step of the process according to the invention, the preferred layer thickness of the reaction mixture, preferably in the form of a liquid film, in the evaporation unit (VD) is preferably not more than 2 cm, more preferably not more than 1 cm, more particularly not more than 0.5 cm and very preferably not more than 0.3 cm.

Carbamatosilanes (CS) are in principle highly volatile and can form hydrogen bonds with the carbamate groups of the silane-terminated polymers (SP). They cannot therefore be removed within an acceptable time frame by conventional distillation, in which a reaction mixture comprising polymer (SP) and carbamatosilane (CS) is stirred in a laboratory flask or a preparation tank. This is true even when the distillation is carried out at high liquidus temperatures under very good vacuum. There is also the problem that high liquidus temperatures can lead to unwanted side reactions, such as discoloration and/or partial degradation of the polymer (SP).

It was found even more surprisingly that carbamatosilanes (CS) can be easily removed from the reaction mixture in the evaporation unit used according to the invention by the process according to the invention, even under surprisingly mild conditions.

Examples of radicals R are alkyl groups such as methyl, ethyl, n-propyl, isopropyl, 1-n-butyl, 2-n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, tert-pentyl; hexyl groups such as n-hexyl; heptyl groups such as n-heptyl; octyl groups such as n-octyl, isooctyl and 2,2,4-trimethylpentyl; nonyl groups such as n-nonyl; decyl groups such as n-decyl; dodecyl groups such as n-dodecyl; octadecyl groups such as n-octadecyl; cycloalkyl groups such as cyclopentyl, cyclohexyl, cycloheptyl and methylcyclohexyl; alkenyl groups such as vinyl, 1-propenyl and 2-propenyl; aryl groups such as phenyl, naphthyl, anthracenyl and phenanthrenyl; alkaryl groups such as o-, m-, p-tolyl; xylyl and ethylphenyl; and aralkyl groups such as benzyl, α- and β-phenylethyl.

Examples of the substituent group R are halogenated alkyl groups such as 3,3,3-trifluoro-n-propyl, 2,2,2,2',2',2'-hexafluoroisopropyl and heptafluoroisopropyl; and halogenated aryl groups such as o-, m- and p-chlorophenyl.

The radical R preferably comprises a monovalent hydrocarbon radical optionally substituted by halogen atoms and having 1 to 6 carbon atoms, more preferably an alkyl radical having 1 or 2 carbon atoms, more particularly a methyl radical.

Examples of radicals R ¹ are hydrogen atoms, the radicals specified for R, and optionally substituted hydrocarbon radicals which are bonded to a carbon atom via nitrogen, phosphorus, oxygen, sulfur, carbon or a carbonyl group.

The radical R ¹ preferably comprises a hydrogen atom or a hydrocarbon radical having 1 to 20 carbon atoms, more particularly a hydrogen atom.

Examples of radical R ² are a hydrogen atom or the examples specified for radical R.

The radical ^R2 preferably comprises a hydrogen atom or an alkyl radical optionally substituted by halogen atoms and having 1 to 10 carbon atoms, more preferably an alkyl radical having 1 to 4 carbon atoms, in particular a methyl or ethyl radical.

Examples of radical R ³ are methyl, ethyl, n-propyl or isopropyl.

The group ^R3 preferably comprises a methyl group or an ethyl group, more preferably a methyl group.

It is advantageous if the radicals R ² and R ³ are identical, since otherwise an exchange of the alkoxy groups on the alkoxysilane radical of formula (I) cannot be ruled out. Identical radicals R ² and R ³ are therefore a preferred embodiment of the invention.

The radical Y preferably has a number average molar mass Mn of at least 200 g/mol, more preferably at least 500 g/mol, more particularly at least 1000 g/mol. The radical Y preferably has a number average molar mass _Mn of at most 40 000 g/mol, more particularly at most 25 000 g/mol, more particularly at most 20 000 g/ _mol .

In the context of the present invention, the number-average molar mass _Mn here is determined by size exclusion chromatography (SEC) against polystyrene standards in THF at 60° C., flow rate 1.2 ml/min, and detection by RI (refractive index detector) on a Styragel HR3-HR4-HR5-HR5 column set from Waters Corp. USA (injection volume 100 μl).

Examples of polymer groups Y are organic polymer groups whose number average molecular weight is from 200 to 40 000 g/mol and whose polymer chain comprises polyoxyalkylenes such as polyoxyethylene, polyoxypropylene, polyoxybutylene, polyoxytetramethylene, polyoxyethylene-polyoxypropylene copolymers and polyoxypropylene-polyoxybutylene copolymers; hydrocarbon polymers such as polyisobutylene and copolymers of polyisobutylene with isoprene; polychloroprene; polyisoprene; polyurethane; polyester; polyamide; polyacrylate; polymethacrylate; vinyl polymer or polycarbonate.

The polymer radical Y preferably comprises polyester, polyether, polyurethane, polyalkylene or polyacrylate radicals, more preferably polyurethane radicals, polyester radicals or polyoxyalkylene radicals, more particularly polyoxypropylene radicals, provided that their number average molecular weight is from 200 to 40,000 g/mol, particularly preferably from 6000 to 22000 g/mol.

The structure of the polymer (OHP) used in the present invention is evident from the possible and preferred definitions described above for the group Y. The polymer (OHP) to be used is preferably a polyurethane or a polyether, preferably with a viscosity of 10 to 1 000 000 mPas, more preferably 1000 to 300 000 mPas. Particularly preferred is polypropylene glycol, preferably with a viscosity of 1000 to 40 000 mPas.

In the context of the present invention, the viscosity is determined after adjustment to 23° C. according to ISO 2555 using a DV 3P rotational viscometer from A. Paar (Brookfield systems) using spindle 5 at 2.5 rpm.

The polymers (OHP) used in the present invention are commercially available products and/or can be prepared by methods commonly used in polymer chemistry.

The isocyanate functional silane (IS) used in the present invention is preferably

OCN(CH ₂ ) ₃ -Si(OCH ₃ ) ₃ , OCN(CH ₂ ) ₃ -Si(OC ₂ H ₅ ) ₃ , OCN(CH ₂ ) ₃ -Si(OCH ₃ ) ₂ CH ₃ , OCN(CH ₂ ) ₃ -Si(OC ₂ H ₅ ) ₂ CH ₃ , OCN(CH ₂ )-Si(OCH ₃ ) ₃ , OCN(CH ₂ )-Si(OC ₂ H ₅ ) ₃ , OCN(CH ₂ )-Si( OCH ₃ ) ₂ CH ₃ or OCN(CH ₂ )-Si(OC ₂ H ₅ ) ₂ CH ₃ , particularly preferably OCN(CH ₂ ) ₃ -Si(OCH ₃ ) ₃ or OCN(CH ₂ )-Si(OCH ₃ ) ₂ CH ₃ .

The silane (IS) used in the present invention is a commercially available product and/or can be prepared by a method commonly used in chemical processes.

In the first process step, the amount of isocyanatosilane (IS) used is preferably such that at least 1.10, more preferably at least 1.15 isocyanate groups are present in the compound (IS) per hydroxyl group of the polymer (OHP).

The first and second process steps are preferably carried out in the presence of a catalyst (K). All catalysts which have been used hitherto for the catalysis of isocyanates with alcohols can be used here.

Preferred examples of catalysts (K) optionally used in the present invention are bismuth-containing catalysts, such as bismuth carboxylates, such as bismuth 2-ethylhexanoate, bismuth neodecanoate or bismuth tetramethylheptanedioate, catalysts comprising other metals in addition to bismuth, especially mixed bismuth-zinc catalysts; tin-containing catalysts, such as dioctyltin dilaurate and dioctyltin oxide, dioctyltin bis(acetylacetonate), dibutyltin dilaurate, dibutyltin oxide, dibutyltin bisacetylacetonate; zirconium-containing catalysts, such as zirconium acetylacetonate; iron-containing catalysts, such as iron acetylacetonate; and acetylacetonates of other metals.

The catalyst (K) optionally used in the present invention more preferably comprises a carboxylate of bismuth, particularly preferably bismuth 2-ethylhexanoate, bismuth neodecanoate or a mixture thereof.

Examples of commercially available catalysts (K) are Kat 22, Kat VP 0243, Kat VP0244 or OMG 315 (all OMG-Borchers), bismuth neodecanoate from Chemos or American Elements, Reaxis MSA 70 or Reaxis C 719 from Reaxis, Catalyst (The Shepherd Chemical Company, USA) and K- K-348 (KING INDUSTRIES, INC., USA).

In the first and second process steps of the invention, the catalyst (K) is preferably used in an amount of 1 to 1000 ppm by weight, more preferably 20 to 600 ppm by weight, and more particularly 60 to 400 ppm by weight. The ppm by weight figures here describe 1 part by weight of catalyst (K) per 1 000 000 parts by weight of reaction mixture. If the first and second process steps are carried out in the presence of a catalyst (K), the catalyst is preferably added during the first process step. Preferably, no further catalyst is added in the second process step, since the catalyst (K) added in the first process step is able to catalyze both process steps.

The components used in the process of the invention may in each case comprise one such component or a mixture of at least a plurality of such components.

The first process step of the invention is preferably carried out at a temperature between 20°C and 180°C, more preferably between 40°C and 150°C, more particularly between 50°C and 120°C.

The second process step of the invention is preferably carried out at a temperature between 20°C and 160°C, more preferably between 30°C and 130°C, more particularly between 40°C and 100°C.

The first and second process steps of the present invention are preferably carried out independently of each other at a pressure of 100 to 2000 hPa, more preferably at a pressure of 900 to 1100 hPa.

In the second process step, the amount of alcohol (A) of the formula (IV) used is preferably such that for each isocyanate group remaining after the first process step, there are at least 1.20, more preferably at least 1.5 and particularly preferably at least 1.8 hydroxyl groups in the alcohol (A).

In this context, it is not necessary to determine the content of isocyanate groups by analysis before the second process step. It is easier to calculate the amount of residual isocyanate groups from the excess isocyanate-functional silane (IS) of the formula (III) used in the first process step. The amount of alcohol (A) used in the second process step mentioned above as preferred, more preferred and more particularly preferred relates to the calculated amount of these isocyanate groups.

During the third process step according to the invention, the reaction mixture is exposed in the evaporation unit (VD) to a pressure of preferably at most 20 mbar, more preferably at most 10 mbar, very particularly at most 5 mbar.

During the 3rd process step according to the invention, the reaction mixture is exposed in the evaporation unit (VD) to a temperature of preferably at most 180°C, more preferably at most 160°C, more particularly at most 140°C.

The third process step according to the invention is preferably carried out such that the reaction mixture has an average residence time in the evaporation unit (VD) of at most 20 minutes, more preferably at most 10 minutes and particularly preferably at most 5 minutes.

All process steps of the present invention are preferably carried out under an inert gas atmosphere, more preferably under argon or nitrogen.

The method of the present invention can of course also have other method steps as well as method steps 1 to 3 of the present invention, and in principle such other method steps can also be performed between method steps 1 to 3. However, preferably, the method of the present invention has no further method steps in addition to method steps 1 to 3 of the present invention.

The process of the invention can be carried out continuously, for example by carrying out the first and second process steps in each case in one or more tubular reactors or loop reactors, in a series cascade of two or more stirred reactors, or in each case in only one stirred reactor, into which new reactants are constantly added and the reaction mixture is constantly discharged. Combinations of two or more types of reactors are also conceivable. In this context, the second reaction step can also be carried out in an unstirred reactor or (intermediate) tank, provided that the necessary mixing of all the raw materials required for this step has been carried out in advance in a suitable mixing unit.

In the first reaction step, the compounds (OHP) and (IS) and any catalyst (K) are preferably metered in together and mixed before or in the reactor unit used in each case. Then, in the second reaction step, the reaction mixture obtained is mixed with the alcohol (A), likewise again before or in the reactor unit used in each case. Further addition of catalyst (K) is possible, but not preferred, since the catalyst used in the first process step can be used to catalyze the second process step.

The third reaction step according to the invention is then carried out in the evaporation unit (VD), preferably likewise continuously. It may be useful here if the apparatus for carrying out the process according to the invention has a buffer tank from which the reaction mixture is metered at a constant rate into the particular evaporation unit (VD) used. It is of course also possible to carry out the third process step separately from the first two process steps in terms of time and/or location.

The process according to the invention can also be carried out batchwise, for example in a stirred reactor in which components (OHP) and (IS) are first reacted with one another in a first process step, optionally in the presence of a catalyst (K), and alcohol (A) is subsequently metered in in a second process step. Although possible, further metering of a catalyst (K) in the second process step is not preferred.

A variant of the batch process according to the invention can also envisage carrying out the first process step in a first reactor, such as a stirred tank, and carrying out the second process step in a second reactor. For a continuous process, stirring of the second reactor is not necessary if the individual reactants are thoroughly mixed beforehand in a separate mixing unit. Thus, here too, the (intermediate) tank can serve as a reactor for the second reaction step.

Even in the case of batchwise implementation of the first two process steps, the third process step according to the invention is preferably carried out continuously in the evaporation unit (VD). In this case, the reaction mixture is preferably metered at a constant rate from an intermediate tank or buffer tank into the particular evaporation unit (VD) preferably used. In this case, it is of course also possible to carry out the third process step separately from the first two process steps in terms of time and/or location.

If the reaction mixture obtained in the second process step still contains alcohol (A), the latter is largely or even completely removed from the reaction mixture together with the carbamatosilane (CS) of the formula (V) in the third process step. After the third process step, the reaction mixture according to the invention therefore comprises preferably at most 3% by weight, more preferably at most 0.1% by weight and more particularly at most 0.05% by weight of alcohol (A), in each case based on the total weight of the reaction mixture.

When used, the catalyst (K) preferably remains in the reaction mixture. After the third process step, the reaction mixture is preferably not subjected to any further workup.

The process of the present invention has the advantages that it is quick and easy to carry out and that readily available raw materials can be used as reactants.

An advantage of the process according to the invention is that the polymer mixtures obtained are free of toxicologically isocyanatosilanes.

An advantage of the process according to the invention is that the polymer mixture obtained contains no or very low amounts of monomeric carbamatosilanes (CS) which could impair the mechanical properties of adhesives, sealants or coatings which can be prepared from the polymer mixture.

Furthermore, the process according to the invention has the advantage that the correspondingly prepared silane-crosslinking polymers are relatively storage-stable and react only very slowly with atmospheric moisture without the addition of additional curing catalysts. This fact is advantageous not only for the storage of the polymers but also for their further processing.

A further advantage of the process according to the invention is that the polymers prepared can be used further directly, for example in the preparation of crosslinkable materials.

The silane-terminated polymers prepared in the present invention can be used anywhere silane-terminated polymers have been used heretofore.

In particular, they are suitable for crosslinkable materials, more particularly for room temperature curable adhesives and sealants, and also for coatings. The preparation of silane-crosslinked coatings, adhesives and sealants from such polymers is widely described in the literature, for example in EP-A 1535940A (paragraphs [0032] to [0054] and Examples 5-7), WO 13079330 A2 (page 27, line 10 to page 40, line 7 and Examples 3-7, 9 and 10), WO 13026654 A1 (page 17, line 28 to page 37, line 24 and Examples 1-9) or WO 11131506 A1 (page 10, line 9 to page 18, line 34 and Examples 1-3). The moisture-curing formulations based on silane-terminated polymers described in these documents, the other ingredients used in this context and the methods for preparing such formulations described therein are likewise considered to be part of the disclosure content of the present description, such as the use of fully formulated coatings, adhesives and sealants described therein.

In the examples described below, all viscosity figures relate to a temperature of 20° C. Unless otherwise stated, the examples below were carried out at ambient atmospheric pressure (in other words, at about 1000 hPa) and at room temperature (in other words, at about 20° C.), or at the temperature that occurs when the reactants are mixed at room temperature without additional heating and cooling.

Example 1a: Preparation of polypropylene glycol having trimethoxysilylpropyl end groups and an average molar mass of 12000 g/mol

A 500 ml reaction vessel with stirring, cooling and heating was charged with 400.0 g (33.33 mmol) of a hydroxyl-terminated polypropylene glycol with an average molar mass _Mn of 12 000 g/mol (commercially available from Covestro AG, Leverkusen (DE) under the name Acclaim 12200), and the initial charge was dried at 80° C. and 1 mbar with stirring for 2 hours. Thereafter, the vacuum was broken with nitrogen. The entire subsequent reaction was carried out under a nitrogen inert gas atmosphere.

For silane termination, the dried polyether was first mixed with 16.42 g (80.00 mmol) of isocyanatopropyltrimethoxysilane (known as GF40 is commercially available from Wacker Chemie AG, Munich (DE)) and then mixed with 0.62 g of Borchi catalyst 315 (a catalyst containing bismuth neodecanoate, from Borchers). This corresponds to a catalyst value of 150 wt ppm based on the total weight of the reaction mixture. After the addition of the catalyst, the reaction mixture is heated directly to 83-84° C. It is then stirred at a temperature of 80° C.

After 60 minutes, the reaction mixture was cooled to 60° C. and 0.64 g (20.00 mmol) of methanol were added. This was followed by stirring for a further 30 minutes. A sample of the reaction mixture was then taken and investigated by IR analysis for any residues of isocyanatosilane still present. This sample contained no isocyanate.

Finally, the sample was passed through a short-path evaporator with a Teflon wiper and internal cooling coil at a metering rate of 160 g/h. The short-path evaporator had a diameter of 8 cm and a length of 26 cm. The wall temperature of the short-path evaporator was 130° C. and the applied pressure was 1 mbar. The final product was collected in the liquid phase discharge of the short-path evaporator. At 411 g, the yield was almost quantitative.

Example 1b: Preparation of polypropylene glycol having trimethoxysilylpropyl end groups and an average molar mass of 12000 g/mol

The procedure was the same as Example 1a with the following modifications:

Between the 2nd process step (reaction with methanol) and the 3rd process step (thin film treatment), a 50 g sample was removed from the reaction mixture.

In the subsequent thin film step of the remaining reaction mixture, the short path evaporator was operated with a wall temperature of 110°C.

Comparative Example 1c (V): Preparation of polypropylene glycol having trimethoxysilylpropyl end groups and an average molar mass of 12000 g/mol

This is a 50 g sample taken from the reaction mixture in Example 1b before the final film step.

Comparative Example 1d (V): Preparation of polypropylene glycol having trimethoxysilylpropyl end groups and an average molar mass of 12000 g/mol

The procedure was the same as Example 1a with the following modifications:

Instead of the final thin-film step, a batch distillation was carried out. For this purpose, the reaction flask in which process steps 1 and 2 were carried out was equipped with a Claisen condenser. Thereafter, the pressure was reduced to 1 mbar and the reaction mixture was heated to 130° C. The vacuum distillation was carried out for 1 hour with vigorous stirring of the reaction mixture and then a sample was taken.

After this time, vacuum distillation was continued for another hour and samples were taken again.

Comparative Example 1e (V): Preparation of polypropylene glycol having trimethoxysilylpropyl end groups and an average molar mass of 12000 g/mol

The procedure was the same as in Example 1d(V) with the following modifications:

Vacuum distillation is carried out at 160°C instead of 130°C.

Example 2: Determination of the properties of the resulting polymer mixture.

The viscosity was measured by the method described in the specification.

The Hazen color value is determined according to ISO 6271 Part 2.

The carbamatosilane (N-(3-trimethoxysilylpropyl)-O-methylcarbamate) content was determined by GC headspace. This method is complicated by two issues:

1. Since the carbamosilane content is very small and depends strongly on the composition of the matrix, it is uncertain whether a uniform calibration curve can be used for all samples.

2. For the generation of the calibration curve, there is a "blank sample" (i.e. a sample completely free of carbamatosilane), since during the first synthesis step itself (i.e. during the reaction of the polymer with the isocyanatosilane) small amounts of carbamatosilane are formed as by-products even without the addition of methanol.

Therefore, in a method that has proven suitable, three 50 g samples are taken from each polymer mixture to be analyzed; of these three samples, one remains unchanged, one is mixed with 0.30 wt. % carbamosilane and one is mixed with 0.60 wt. % carbamosilane. When these three samples are subsequently measured by headspace GC, the integration of the individual carbamosilane peaks results in three equations with two unknowns (A1 = x*c; A2 = x*(c+0.3); A3 = x*(c+0.6); where A1, A2 and A3 are the integrated peak areas, x is the proportionality factor and c is the target concentration of carbamosilane). The carbamosilane peak here is easily detectable because it is the only peak that significantly distinguishes the GC spectra of the three samples.

Since even two equations with two unknowns can be solved mathematically, three solutions for the concentration c can be calculated here due to the different combination possibilities. These three solutions must of course produce the same result within the measurement accuracy, i.e. an error tolerance of ±10% of the respective measured value for the carbamatosilane content. If this is not the case, the measurement must be repeated.

Note: Since the exact metering of such small amounts of carbamatosilane as described above is not easy in practice, it is also possible to operate with slightly different metering amounts. Just pay attention to this difference and enter the exact value measured into the corresponding equation. In other words, if, for example, 0.32 wt. % is accidentally metered instead of the expected 0.30 wt. %, the measurement can still be continued. However, in the final calculation, the corresponding equation must be A2=x*(c+0.32).

To perform the headspace measurement, 0.5 g of sample was weighed into a 20 ml headspace vial, which was carefully purged with nitrogen for about 30 seconds before being closed. The vial was subsequently heated at 150° C. for 30 minutes and the gas mixture above the sample was then fed directly into the GC via a thermal transfer capillary at 170° C. All samples were measured in duplicate in each case.

Using the polymer mixtures prepared in Examples 1a to 1e, the following results listed in Table 1 were obtained.

Table 1:

*Examples labeled "1 h" describe samples after 1 hour of distillation time, and examples labeled "2 h" describe samples after 2 hours of distillation time.

Example 3: Preparation of polypropylene glycol having trimethoxysilylpropyl end groups and an average molar mass of 18000 g/mol

The procedure was the same as in Example 1b with the following modifications:

Instead of 400.0 g of hydroxyl-terminated polypropylene glycol having an average molar mass M _n of 12 000 g/mol, 400.0 g (22.22 mmol) of hydroxyl-terminated polypropylene glycol having an average molar mass M _n of 18 000 g/mol (commercially available under the name Acclaim 18200 from Covestro AG, Leverkusen (DE)) were used.

- Instead of 16.42 g (80.00 mmol) of isocyanatopropyltrimethoxysilane, 10.95 g (53.33 mmol) of the same isocyanatosilane were added dropwise.

- Instead of 0.64 g (20.00 mmol) of methanol, only 0.43 g (13.33 mmol) of methanol was used.

After the second process step (ie the reaction with methanol) was completed, a 50 g sample ("Sample 1") was taken.

The remaining amount of product was subjected to the third process step (thin film treatment at 110° C.) as described in Example 1b. The product obtained in that step is referred to as “Sample 2”.

All other parameters remain unchanged.

Example 4: Determination of the properties of the resulting polymer mixture.

The viscosity, hessen value and carbamatosilane (N-(3-trimethoxysilylpropyl)-O-methylcarbamate) content were also determined as described in Example 2.

Using the samples produced in Example 3, the following results listed in Table 2 were obtained.

Table 2:

Example 3 Sample 1 (comparison) Sample 2 Temperature in step 3 [°C] -- 110 Viscosity [Pas] 26.3 26.5 Hazen color value 13 13 Carbamate silane content [wt%] 0.49 0.039

Example 5: Preparation of polypropylene glycol having α-methyldimethoxysilylmethyl end groups and an average molar mass of 12000 g/mol

The procedure was the same as Example 1a with the following modifications:

Instead of 16.42 g (80.00 mmol) of isocyanatopropyltrimethoxysilane, 12.90 g (80.00 mmol) of α-isocyanatomethylmethyldimethoxysilane (available from Wacker Chemie AG, Munich (DE) under the name XL 42 commercially available).

After the second process step (ie the reaction with methanol) was completed, a 50 g sample was taken ("Sample 1").

The remaining amount of product was subjected to the third process step (thin film treatment) as described in Example 1a, with the short path evaporator being operated at a wall temperature of 90° C. The product obtained in this step is referred to as “Sample 2”.

All other parameters remain unchanged.

Example 6: Determination of the properties of the resulting polymer mixture.

The viscosity and Hazen value of the sample from Example 5 were also determined as described in Example 2. The α-N-(methyldimethoxysilylmethyl)-O-methylcarbamate content was determined in an equivalent manner to the determination of the carbamatosilane described in Example 2. The only difference was, of course, that the headspace GC peak analyzed was that of the carbamatosilane to be determined here.

Using the samples produced in Example 5, the following results listed in Table 3 were obtained.

Table 3:

Example 5 Sample 1 (comparison) Sample 2 Temperature in step 3 [°C] -- 90 Viscosity [Pas] 7.1 7.1 Hazen color value 8 8 Carbamate silane content [wt%] 0.59 0.057

Example 7: Preparation of polypropylene glycol having α-methyldimethoxysilylmethyl end groups and an average molar mass of 18000 g/mol

The procedure was the same as in Example 5, with the following modifications:

Instead of 400.0 g of hydroxyl-terminated polypropylene glycol having an average molar mass M _n of 12 000 g/mol, 400.0 g (22.22 mmol) of hydroxyl-terminated polypropylene glycol having an average molar mass M _n of 18 000 g/mol (commercially available under the name Acclaim 18200 from Covestro AG, Leverkusen (DE)) were used.

- Instead of 12.90 g (80.00 mmol) of α-isocyanatomethylmethyldimethoxysilane, 8.60 g (53.33 mmol) of the same isocyanatosilane were added dropwise.

- Instead of 0.64 g (20.00 mmol) of methanol, only 0.43 g (13.33 mmol) of methanol was used.

As in Example 5, here too, after the end of the second process step (ie the reaction with methanol), a 50 g sample ("sample 1") was taken.

The remaining amount of product was subjected to the third process step (thin film treatment at 110° C.) as described in Example 1b. The product obtained in that step is referred to as “Sample 2”.

All other parameters remain unchanged.

Example 8: Determination of the properties of the resulting polymer mixture.

The viscosity, the haze value and the carbamatosilane (α-N-(methyldimethoxysilylmethyl)-O-methylcarbamate) content were also determined as described in Example 2.

Using the samples produced in Example 7, the following results listed in Table 4 were obtained.

Table 4:

Claims (8)

1. a process for preparing silane-terminated polymers (SP) of the formula (I),

Y-[O-C(＝O)-NH-(CR ¹ ₂ ) _b -SiR _a (OR ² ) _3-a ] _x (I)，

it is characterized in that the method comprises the steps of,

in process step 1, at least one polymer of formula (II) (OHP)

Y-[OH] _x (II)

With at least one isocyanate-functional silane (IS) of formula (III)

O＝C＝N-(CR ¹ ₂ ) _b -SiR _a (OR ² ) _3-a (III)

Provided that the isocyanate functional silane (IS) IS used in such an amount that at least 1.05 isocyanate groups are present in the silane (IS) per hydroxyl group in the compound (OHP),

wherein the method comprises the steps of

Y is a polymer group of valence x,

r may be the same or different and are monovalent, optionally substituted hydrocarbon radicals,

R ¹ may be the same or different and is a hydrogen atom or a monovalent, optionally substituted hydrocarbon group,

R ² may be the same or different and is a hydrogen atom or a monovalent, optionally substituted hydrocarbon group,

x is an integer of 1 to 50,

a may be the same or different and is 0, 1 or 2, and

b may be the same or different and are integers of 1 to 10,

subsequently in process step 2, the unreacted isocyanate groups of the silane (IS) are reacted in the reaction mixture obtained in process step 1 with at least one alcohol (A) of the formula (IV)

R ³ OH(IV)，

Wherein the method comprises the steps of

R ³ Is a hydrocarbon group having 1 to 4 carbon atoms,

and subsequently in a3 rd process step the reaction mixture obtained in the 2 nd process step is passed through an evaporation unit (VD) in which the reaction mixture having a layer thickness of not more than 5cm is exposed to a pressure of at most 80 mbar and a temperature of at most 200 ℃, wherein the Carbamatosilane (CS) formed in the second process step of formula (V) is at least partially evaporated and removed,

R ³ O-C(＝O)-NH-(CR ¹ ₂ ) _b -SiR _a (OR ² ) _3-a (V)

all variables in formula (V) have the above definition.

2. The process according to claim 1, characterized in that the carbamatosilane content in the reaction mixture obtained after the process of the invention is at most 0.3% by weight, based on the total weight of the reaction mixture.

3. The process according to claim 1, characterized in that the carbamatosilane content in the reaction mixture obtained after the process of the invention is at most 0.1% by weight, based on the total weight of the reaction mixture.

4. A process according to one or more of claims 1 to 3, characterized in that the Isocyanatosilane (IS) IS used in process step 1 in such a way that for each hydroxyl group of the polymer (OHP) at least 1.10 isocyanate groups are present in the compound (IS).

5. The process according to claim 1, characterized in that the process steps 1 and 2 are carried out in the presence of a catalyst (K).

6. The method according to claim 1, characterized in that the 3 rd method step is performed such that the reaction mixture has an average residence time in the evaporation unit (VD) of at most 20 minutes.

7. The method according to claim 1, characterized in that the reaction mixture during the 3 rd method step in the evaporation unit (VD) is exposed to a temperature of at most 180 ℃.

8. The method according to claim 1, characterized in that all method steps are carried out under an inert gas atmosphere.